Let the app choose mp3 or 3gp audio files when necessary

What if you install an app that might have some 3gp audio packaged in it, or distributed along with an SD card with the full audio collection? What happens later when you would prefer the higher quality mp3 audio? Or what if your app was originally looking for mp3 audio on the device but can’t find it so it searches the internet where it finds the audio files, but they are in 3gp format? The audio cannot be played.
I envision an app that is smart enough to figure out that if the filename is correct but the extension is wrong it can make the adjustment and still play the audio in either format. Of course as a devleoper you might only make one format available or force the app to choose a single format.